Histological Phenotyping in Eosinophilic Esophagitis: Localized Proximal Disease Is Infrequent but Associated with Less Severe Disease and Better Disease Outcome

Introduction: It is still unknown whether eosinophilic esophagitis (EoE) patients with localized disease are different from those with extended disease. Methods: We evaluated prospectively included patients in the Swiss EoE cohort. Data on all patients with active disease at baseline, no concomitant gastroesophageal reflux disease, no strictures at baseline, and at least one follow-up visit were analyzed. We compared patients with histologically localized proximal versus distal versus extended (=proximal and distal) disease with regard to patient, disease characteristics, disease presentation, and development of complications. Results: We included 124 patients with a median of 2.5 years of follow-up (73.4% males, median age 35.0 years). Ten patients had proximal (8.1%), 46 patients had distal (37.1%), and 68 patients had extended disease (54.8%). Patients with proximal disease were significantly more often females (80%) compared with patients with distal (26.1%, p = 0.002) or extended disease (19.1%, p < 0.001) and reported less severe symptoms (VAS 0 vs. VAS 1, p = 0.001). Endoscopic and histological disease was less pronounced in the proximal esophagus of proximal EoE compared to extended disease (EREFS 1.0 vs. 3.0, p = 0.001; 27.0 eos/hpf vs. 52.5 eos/hpf, p = 0.008). Patients with proximal disease were less likely to undergo dilation compared to patients with distal disease in the follow-up (3.3% vs. 23.3%, p = 0.010). In a multivariate Cox regression model, proximal eosinophilia was less likely to be associated with treatment failure compared to distal eosinophilia. Conclusion: Although isolated proximal EoE is infrequent, it is associated with less severe disease and better disease outcome. Proximal disease appears to present a unique EoE phenotype.